A flexographic printing machine is one type of printing machines that constantly manage ink in a proper state by circulating the ink.
A flexographic printing machine provides therein an ink fountain so as to be in contact with the surface of an ink-applying roll called an anilox roll. Ink in the ink fountain is supplied to very fine dimples or holes called cells formed on the surface of the anilox roll, is further supplied from the cells to a printing cylinder having a relief being formed of rubber or synthetic resin at its outer circumference, and is finally transferred onto a sheet to be printed.
Using flexo ink, such a flexographic printing machine circulates the flexo ink by supplying the flexo ink from an ink supply source to the ink fountain through an ink supply pipe and also reclaiming the flexo ink from the ink fountain to the ink supply source through an ink reclaiming pipe. Thereby, the flexo ink in the ink fountain is kept kinetic, so that solidification of the flexo ink is prevented and the printing process can be carried out without interruption.
Various types of flexographic printing machines are provided such as: a two-roll flexographic printing machine in which an ink fountain is formed at a space on the nip contact between an anilox roll and a doctor roll that is formed by wrapping rubber around an iron core (see Patent Literature 1); and a chamber-type flexographic printing machine that forms an ink fountain at a space called a chamber formed by an anilox roll and a doctor blade being in contact with the anilox roll.
Patent Literature 1 describes the technique that relates to a two-roll flexographic printing machine. This technique aims at rapidly washing off ink remaining in the ink fountain and ink transferring pipes and generates an adequate amount of air flow to remove ink remaining on the inner walls of the ink transferring pipes downstream from the ink fountain to the pipes. This rapidly removes remaining ink when ink color is to be changed.
Besides a flexographic printing machine, a continuous-type ink-jet printer is an exemplary of a printing machine that circulates ink during the printing process.
Patent Literature 2 describes a technique that relates to such an ink-jet printer circulating ink during the printing process. The disclosed technique is to jet ink supplied from an ink tank storing the ink through a print head towards an object to be printed and reclaims jetted ink which has not been used for printing to restore the ink into the ink tank.
This technique involves an improving solution to problems caused when the ink in the tank foams. Specifically, since such generated foam in the tank stay on the surface of the liquid-form ink, the presence of foam makes it difficult to detect an amount of ink remaining in the tank. Furthermore, when an adequate amount of liquid-form ink is stored, foam only on the surface of the liquid-form ink do not enter the main tank, but when the liquid-form ink has exhausted, the foam also flow into the main tank.
As a solution, Patent Literature 2 provides a front receiving tank disposed upstream of the ink tank in the direction of ink collection; foaming inhibiting means that lessens foaming of the ink when the ink is being collected into the front receiving tank; and a connecting pipe that connects the bottom of the front receiving tank and the bottom of the ink tank in ink collecting means that reclaims the ink, aiming at less ink foaming. The foaming inhibiting means applies a spraying mechanism that sprays collected ink toward the inner wall of the front receiving tank or the surface of the ink so that the spray of ink surely hits the foam on the surface of the liquid-form ink and thereby efficiently breaks the foam.